Brake control apparatus

ABSTRACT

Brake control apparatus utilizing vehicle weight or gravitational force as the primary force for applying the vehicle brakes. The gravitational force is transmitted by a fulcrum lever acting through a fluid medium, the moment arms or fulcrum point of said lever, and therefore the force delivered thereby, being variable according to the deflection of the vehicle springs reflecting the vehicle weight and its load, as well as the effect of vertical oscillations of the wheels during movement of the vehicle over a running surface, thereby controlling the degree of brake shoe pressure on the wheels according to the effective friction of the wheels with the running surface.

United States Patent 11 1 188/195; l80/DIG. l, 100

5/1970 Farmer-y et al. 303/22 A Oshida et al. 1 Nov. 6, 1973 BRAKECONTROL APPARATUS [75] Inventors: Yasunosuke Oshida; Seisho Pmfmry '.'f{zeger Okamoto; Ei lchi Shinomiya, all of Asslstam Emmmer m er KobeJapan Att0mey-Ralph W. Mclntire, Jr. [73] Assignee: The Nippon Air BrakeCo., Ltd., 1571 ABSTRACT Kobe Japan Brake control apparatus utilizingvehicle weight or [22] Filed: Sept. 18, 1972 gravitational force as theprimary force for applying the vehicle brakes. The gravitational forceis transmitted [2]] Appl' 2902l6 by a fulcrum lever acting: through afluid medium, the

moment arms or fulcrum point of said lever, and there- [52] [1.8. CI.303/22 R, 188/195 fore the feree delivered y, being var a l a c rd- [51]Int. Cl B60t 8/18 g t deflection 0f h vehicle p g reflecting the [58]Field of Search 303/22 R, 22 A; vehicle weight and its load, as well asthe effect of vertical oscillations of the wheels during movement ofthevehicle over a running surface, thereby controlling the degree ofbrake shoe pressure on thewheels according to the effective friction ofthe wheels with the running surface.

13 Claims, 1 Drawing Figure TO BRAKE CYLINDER PATENTEDNHV 6 I975 T0BRAKE CYLINDER BRAKE CONTROL APPARATUS BACKGROUND OF THE INVENTION Thecoefficient of friction between two bodies differs greatly depending onwhether the contact between such bodies is static or moving. Thecoefficient of static friction is primarily only proportional'to thecontact pressure, compared to which variations in other elements, forexample the pressure contact surface area, etc., are so minor as to besecondary. It is virtually a constant thing. The coefficient of movingfriction, howcase, to avoid changes in the friction state at the contactsurface. I I I Thus, during rolling contact the coefficient of frictionY is that of static friction or something approximating it.

ever, is smaller than that of static friction and is said to becomesmaller as the relative velocity'increases.

Braking of railway vehicles, that is to say restraining the torsion ofthe wheel axles, is usually brought about by the force of friction thatdevelops as a result of pressure contact by a brake shoe. In suchinstances, however, if this friction or adhesion, exceeds that on therunning surface between the wheel and the track, the

i that coefficient is extremely important in the operation of brakes.

Moreover, in the past, the friction between the wheels and the track orthe coefficient of adhesion, has been calculated from such measuredvalues as the running speed and the commencement of braking, the

braking distance and the braking force, etc. It has been found that suchcoefficient of adhesion reduces greatly concurrently with increases inthe running speed of the cars. It has become the general practice toprevent the wheels from sliding by limiting the vehicle braking force onthe basis of this calculated coefficient of adhesion. To state this inanother way, despite the fact that it would be possible to reducebraking distance by using a greater braking force, it has become thetendency in practice to reduce braking force to an extent in excess ofthat normally necessary in order to prevent the wheels from sliding.

Here, the present inventors noted that the aforesaid calculated frictionor adhesion, which had come to be thought of as varying with runningspeed is only apparent and that the true coefficient of friction doesnot vary that much. To restate this, the pressure contact between thewheel and the track, that is to say, the force which has generally beenthought to be proportional to the vehicle weight and thus constantduring movement is not actually so. It varies together with the verticaloscillations of the wheels during movement. The inventors furtherobserved that this state of vertical oscillation becomes violent withincreases in running speed. Even were the braking force, that is to saythe contact pressure between the brake shoe and the wheel constant,while the contact pressure between the wheel and the track varied, itwould be impossible to maintain rolling contact between the wheel andthe running surface, making it possible for the wheel to slide. THeythus noted that it is impossible, in such a However, even ifmomentarily, slipping begins, the coefficient of friction changes tothat of moving friction and therefore drops Thus, at high speedoperations, there is a constant alternation between rolling and slidingat the point of contact between the wheels and the track. It must beconcluded, therefore, that, as stated before, the coefficient offriction during running of the wheel decreases with increases in rollingspeed thereof. As the gravity deriving from the weight of the car isused as the brake power source in'the present invention, there is noneed for a special power source for the brakes. Specifically, in thepast, operators have controlled braking by varying the conversion ratebetween gravity and braking power. It goes without saying, however, thata power source is necessary to drive the controls. In the presentinvention, compressed air or pneumatic pressure is used only foroperating-the controls. The quantity required is dramatically less thanhas been needed in the past and this is an additional benefit of thepresent invention.

SUMMARY OF THE INVENTION Specifically,'the object of the presentinvention is to maintain rolling contact of the wheels with the runningsurface and prevent sliding by varying the braking force, that is, thecontact pressure of the brake shoe on the wheel, in accordance with thevertical oscillations of the wheel during running thereof, as above exvplained, so as to permit the use of the overall maximum braking force,it being understood that the truck moves upwardly relative to the wheelswhen the contact pressure between the track and the wheel is great and,conversely, moves downwardly when such contact pressure is reduced.Therefore, it is also the object of the changes in gravitational forceto the changes in the upward and downward movement or verticaloscillations of the wheels and thereby make it possible'to lower thelimits of braking force to a degree less than that provided heretoforeby other known anti-wheel-slide devices, thus providing improved brakingeffects and reduced braking distance.

The invention herein disclosed utilizes the gravitational force providedby the weight of the vehicle for exerting a braking force on the brakeshoes by acting through a hydraulic o'r incompressible medium. Thegravitational force is applied to one end of an operating lever and istransmitted to the hyraulic medium by the other end of said lever actingon the piston of a master brake cylinder, said lever having a movablefulcrum so as to transmit said gravitational force to the mastercylinder at a ratio determined by the position of a fulcrum memberrelative to the moment arms of the lever.

A conventional brake pipe nd auxiliary reservoir arrangement is employedin conjunction with a pneumatic-to-hydraulic pressure converter whichoperates responsively to pneumatic pressure supplied from the auxiliaryreservoir, when a brake pipe pressure reduction is effected to place anisolated portion of the hydraulic medium under pressure at a degreecorresponding'to the degree of brake pipe pressure reduction. Theisolated pressurized hydraulic fluid acts on and operates the fulcrummember to a position determined by the degree of pressure of thehydraulic fluid, thereby establishing the relative lengths of the momentarms of the operating lever and the ratio or degree of gravitationalforce transmitted to the master brake cylinder. Since the braking forceis thus established in accordance with the gravitational force or weightof the vehicle cooperatively with the degree of hydraulic fluid pressureestablished by brake pipe pressure reduction, any variations of thegravitational force due to vertical oscillations of the wheels on unevenor otherwise affected running surfaces (which determines the coefficientof moving friction) is automatically reflected in the braking forcetransmitted to the brake shoes so that such braking force is alwayscompatible with the running friction of the wheels.

The single FIGURE drawing is an elevation view, mostly in section andwith a certain portion thereof in perspective, of a brake controlaparatus embodying the invention.

DESCRIPTION AND OPERATION As shown in the drawing, the brake controlapparatus comprises, generally, a car gravity transmission section A, agravity braking force ratio converter section B, apneumatic-to-hydraulic pressure converter section C, a hydraulicpressure check valve section D, and a pneumatic pressure drive sectionE.

An unsprung portion of the vehicle comprises a wheel I mounted on anaxle 2 for rotation therewith, said axle being rotatably supported in ajournal box 3. A vehicle load spring 4 is supported on the journal box 3for flexibly supporting a sprung portion of the vehicle comprising thevehicle body a portion of which is represented at 5. The car gravitytransmission section A comprising a linkage system is operably disposedbetween the sprung and unsprung portions of the vehicle 7 andspecifically comprises a torque rod 6 which is disposed parallel towheel axle 2 and is axially rotatably supported on the car body 5. Thetransmission section A further comprises two torque arms 7 and 8 axiallyspaced on torque rod 6 in perpendicular relation thereto, said torquearms being fixed at respective ends to said torque rod for rotationtherewith. The other end of torque arm 7 is connected to one endofconnecting rod 9, the other end of said connecting rod being connectedto load spring 4 for transmitting the deflections of said spring to saidtorque arm and thereby effecting rotation of the torque rod 6 inaccordance with the'deflections of said spring.

The sections B, C, D, and E are all housed within a casing 10 which issecured to another portion of the car body 5.

The gravity braking force ratio converter section B comprises a transferpiston l l sealingly and slidably operable within a bore 12 formed incasing 10, one end of said piston extending outside of the casing so asto be in contact with the end of torque arm 7 opposite torque rod 6. Theopposite end of piston 11 extends to the inside of casing 10 into ahydraulic fluid chamber 13 for operatively engaging one end of anoperating lever 14 disposed in said chamber, said one end of said leverbeing subjected to a gravitational force acting in an upwardlydirection, as viewed in the drawing, and as transmitted thereto throughsaid piston from the torque arm 7 of the transmission section A.Hydraulic cham- I ber 13 acts as a storage reservoir for hydraulic fluidwhich is open and maintained at atmospheric pressure via a fluid levelguage 15.

The end of operating lever 14 opposite transfer piston 1 l is retainedby a spring-biased pressure device 16 in pressure contact with one sideof a pressure piston 17 of a master cylinder device 18, the oppositeside of said piston being in contact with hydraulic fluid in a brakecylinder conduit 19 for transferring to said hydraulic fluid a forceexerted on said piston by said opposite end of said lever in adownwardly direction, as viewed in the drawing, and in a manner to behereinafter explained.

The gravity braking force converter B further comprises amovable fulcrummember 20 axially displaceable in a substantially parallel relation tooperating lever 14, said fulcrum member having a pair of rollers 21disposed in one end thereof in an over-and-under fashion with the lowerroller making rolling contact with the upper side of said operatinglever opposite the side in contact with transfer piston 1 l and masterbrake cylinder piston 17. The upper roller 21 is in rolling contact witha buffer plate 22 fixed in casing 10 in a spaced-apart parallel relationto operating lever 14, the spacing distance between the buffer plate andthe operating lever being substantially equal to the total diameters ofthe two rollers to permit snug rolling motion thereof with a minimum offriction between the buffer plate and the operating lever during axialdisplacement of the fulcrum member. The axial position of fulcrum member20 and therefore of the rollers 21 relative to operating lever 14determines the fulcrum point of said lever and the respective lengths ofthe moment arms of the lever. Thus a gravitational force exerted by thevehicle on the transmission sectionA and applied by the transfer piston1 1 to the adjacent end of operating lever 14 causes a brake-applyingforce to be exerted by the other end of said lever to master cylinderpiston 17 at a ratio determined by the respective lengths of the momentarms of said lever.

The roller-supporting end of fulcrum member 20 is connected to one endof a piston rod 23 which is sealingly and slidably supported in a guidebore formed in a separating wall 24 formed internally of casing 10 forseparating hydraulic chamber 13 from a pneumatic pressure controlchamber 25 surrounding said piston rod. A drive piston 26 is carried bythe other end of piston rod 23 which also has an internally formedrecess 27 opening to the exterior of the piston rod by a radiallydisposed passageway 28 adjacent the piston end. Recess 27 is open at itsopposite end to hydraulic chamber 13 via a radially disposed passageway29 formed in piston rod 23. An axially disposed passageway 30 connectsthe opposite faces of drive piston 26, said passageway having tworadially disposed openings 31 and 32 which open to the exterior ofpiston rod 23 adjacent said drive piston. Opening 32 is formeddiametrally opposite passageway 28.

A tubular valve member 33 is coaxially slidably carried on the exteriorof piston rod 23. One end of valve member 33 normally abuts againstdrive piston 26 and the opposite end is sealingly slidably guided in aseparating wall 34 formed internally of casing 10 for separatingpneumatic pressure control chamber 25 from a hydraulic pressure controlchamber 35 surrounding the outer side of said valve member between-saiddrive piston and separating wall 24. A spring 36 compressed betweenseparating wall 24 and valve member 33 normally retains said valvemember in abutting contact with drive piston 26 and, consequently, thefulcrum member 20 in a neutral position, in which it is shown in thedrawing and in which the rollers 21 are positioned directly in axialalignment with transfer piston 11, so that in said neutral position theeffects of gravitational force of the vehicle are not transmitted vialever 1-4 to master cylinder 18.

Valve member 33 has at the end adjacent drive piston 26 an internallyformed annular groove 37 which is in registry with radial passageways 28and 32 to place said passageways in communication with each other whensaid valve member is in abutting contact with drive piston 26. Thus,with valve member 33 in this abutting position, hydraulic fluid fromhydraulic chamber 13 at atmospheric pressure is communicated via radialpassageway 29, recess 27, radial passageway 28, annular groove 37,radial opening 32, and axial passageway 30 to a hydraulic pressureoperating chamber 39 only. A floating piston 43 sealingly separateshydraulic fluid chamber 39 from a pneumatic pressure chamber 44.Floating piston 43 is normally biased by a spring 45 disposed in chamber39 to a pressure-free or slack position. When pressure in chamber 44 isat atmospheric pressure, spring 45 is effective for moving piston 43upwardly, as viewed in the drawing, during which movement hydraulicfluid is drawn from chamber 13 via passageway 41 past check valve 42into chamber 39 so as to keep the variable volume of said chamber 39constantly filled with a solid column of hydraulic fluid regardless ofthe position of floating piston The check valve device D comprises ahydraulic fluid delivery chamber 46, to which brake cylinder conduit 19opens, and a hydraulic fluid supply chamber'47 constantly incommunication with hydraulic fluid chamber 39 via a passageway 48. Acheck valve 49, which is interposed between supply chamber 47 anddelivery chamber 46, is operable either to an unseated or open position,in which said supply and delivery chambers are in communication witheach other, or to a closed or seated position on a valve seat 50 forcutting off said communication between said supply and deliverychambers.

Check valve 46 is urged in one direction toward its seated position by aspring 51 disposed indelivery chamber 46. A valve stem 52 extendsaxially from check valve 49 through supply chamber 47 to normally makeabutting contact with an axially aligned, valveoperating piston 53. Oneside of valve-operating piston 53 adjacent hydraulic fluid supplychamber 47 is subject to the hydraulic pressure prevailing in saidsupply chamber while the opposite side of said piston is adjacent to andsubject to hydraulic fluid at atmospheric pressure in a balancingchamber 54 open to hydraulic chamber 13 via a passageway 55.Valve-operating piston 53 is urged by a spring 56, disposed in balancingchamber 54, to a contact position relative to valve stem 53 in whichvalve 49 is operated to its open position, said valve-operating pistonbeing operable by prevail ing hydraulic pressure in supply chamber 47sufficient for overcoming spring 56, to a detached position out ofcontact with valve stem 52 and in which valve 49 is operated to itsclosed position.

The'pneumatic or air pressure drive section E comprises an auxiliaryreservoir 57 which is chargeable with compressed air from a brake pipe58 when said brake pipe is charged in well-known manner. The brake pipe58 is connected to a passageway 59 which opens to a charging chamber 60of the drive section E. Charging chamber 60 is separated from anequalizing chamber 61 by a diaphragm-valve member 62 having 7 acentrally disposed aperture 63 for communicating the opposite sides ofsaid diaphragm with each other.

Three check valve devices 64, 65, and 66 are operably disposed incharging chamber 60. Check valve device 64 is interposed in passagemeans comprising passageway segments 67 and 68 for controllingcommunication between auxiliary reservoir 57 and pneumatic pressurechamber 44 of the pneumatic-to-hydraulic pressure converter C andbetween said chamber and atmosphere. Check valve device 65 is interposedin passage means comprising passageway segments 69, 70, and 71 forcontrolling communication between charging chamber 60 and pneumaticpressure chamber 25 of the gravity braking force converter B and betweensaid pneumatic pressure chamber and atmosphere. The pneumatic pressuredrive section E also comprises an emergency reservoir 72 connecting witha passageway 73. Check valve device 66 is interposed between passageway73 and passageway segments 70, 71 for controlling communication betweenemergency reservoir 72 and pneumatic pressure chamber 25, via

passageways 71 and 73, for controlling communication between saidemergency reservoir and atmosphere via passageways 73,71 and check valvedevice 65, and for controlling communication between charging chamberand said emergency reservoir via check valve device and passageways 70,73.

The check valve devices 64, 65, and 66 have operating pistons 74, 75,and 76 for operating valve members 77, 78, and 79 to unseated or openpositions, said valve members being biased by springs 80, 81, and 82 toseated or closed positions, respectively. Piston 79 of check valvedevice 66 is subject to pneumatic pressure in charging chamber 60 andoperable responsively thereto in a left hand direction, as viewed in thedrawing, for effecting unseating of valve member 79. A pin 83 limitsleftward movement of piston 76 so as to prevent closing olT the ends ofpassageways and 71 communicating with each other through the pistonchamber.

Each of the operatingpistons 74 and of check valve devices 64 and 75 areprovided with axially disposed passageways 84 and 85 extending throughtheir entire lengths for communicating the ends of said pistons adjacentthe valve members 77 and 78 withatmospheric vent ports 86 and 87,respectively.

Check valve devices 64 and 65 are disposed parallel to each other sothat an operating bar 88 may extend ther'ebetween with the opposite endsof said bar engaging respective grooves formed in the pistons 74 and 75.Operating bar 88 carries a cylindrical spring housing 89 closed at theright hand end, as viewed in the drawing, and extending transverselyfrom the midpoint of said bar at which said housing is fixed. A spring90 enclosed within housing 89 and compressed between the closed endthereof and an internal wall of casing 10, serves to bias bar 88 andsaid housing in a right-hand direction so as to have said closed endnormally in contact with diaphragm 40 at a point coinciding withaperture 63.

The rightward movement of bar 88 and therefore spring housing 89 islimited to an amount such that when said housing makes contact withdiaphragm-valve member 62, said diaphragm-valve member is not extendedby said rightward movement beyond a plane coinciding with the unstressedor relaxed position of the diaphragm-valve. Movement of bar 88 andtherefore of operating pistons 74 and 75 in a left-hand direction, aswill hereinafter be more fully described, is limited to an amount suchthat leftward movement of said pistons does not close off the openingsof passageways 68 and 67 into the piston chambers of check valve devices64 and 65, respectively.

In considering the operation of the apparatus embodying theinvention,'the following assumptions are made: (1) brake cylinderconduit 19 is filled with unpressurized hydraulic fluid so that thevehicle brakes are in a released condition; (2) chamber 39 below piston43 is filled with hydraulic fluid; (3) a suitable quantity of hydraulicfluid, as indicated by the hydraulic fluid level gauge 15, is maintainedin chamber 13 at atmospheric pressure; (4) the car weight is transmittedto torque rod 6 so that a gravitational force proportional to the carweight acts on transfer piston 11; and all operating parts of thepneumatic pressure drive section B are in the respective positions shownin the drawing.

If in this state of the apparatus brake pipe 58 is charged withcompressed air at a predetermined normal pressure such as 72 psi., forexample, this compressed air also flows into charging chamber 60 to theleft side of diaphragm 62. Since check valve 78 is seated, pneumaticpressure in chamber 60 initially builds up and becomes effective formoving diaphragmvalve member 62 to the right out of contact with springhousing 89 so that pneumatic pressure may flow through aperture 63 intoauxiliary reservoir 57, whence it may flow into passageway 67. But sincecheck valve 77 is also seated, pneumatic pressure in auxiliary reservoir57 continues to build up until the pressure in said auxiliary reservoirand in brake pipe 58 equalizes, at which point diaphragm-valve member 62reverts to an unstressed or relaxed position in contact with springhousing 89.

The right-hand side of piston 76 of check valve device 62 is subjectedto brake pipe pressure in charging chamber 60. Since the left-hand sideof piston 76 at this time is open to atmosphere via passageway 70 andaxial passageway 85 through piston 75 of check valve device 65, piston76 is moved to the left, opening check valve 79. If, at this time, thereis any residual pressure in emergency reservoir 72, such residualpressure is discharged to atmosphere, together with that in pneumaticpressue chamber 25 of section B, via passageways 73, 71, and 70, andthence through check valve device check valve device 64 is also open toatmosphere past the unseated valve seat on its left and, through axialpassageway 84 and through atmospheric port 86, chamber 44 of section Cis also at atmospheric pressure. With chamber 44 at atmosphericpressure, spring 45 is effective for moving piston 43 to its uppermostlimit, during which movement hydraulic fluid is drawn from hydraulicchamber 13 through check valve 42.

The drive piston 26 of the gravity braking force converter B is normallybiased in a left-hand direction to a neutral position by the force ofspring 36 acting through valve member 33. Since, in this neutralposition of drive piston 26, the position of rollers 21, and thereforethe fulcrum point of lever 14, coincides with the vertical axis oftransfer piston 11, all of the gravitational force acting on said pistonis transmitted to the buffer plate 22. None of the gravitational force,therefore, is transmitted through lever 14 to the master brake cylinderdevice 18. Since spring 56 of hydraulic pressure check valve section Dat this time, acting through piston 53 and valve stem 52, is holdingcheck valve 49 in its open position, in which chamber 39 (now atatmospheric pressure) is in communication with master cylinder 18, thehydraulic fluid in said master brake cylinder is also at atmosphericpressure.

A reduction of pressure in brake pipe 58, which, as previously noted,had been charged to a pressure of 72 psi., may be effected to a degreesufficient for obtaining the desired braking effect. If an initial,or'what may be called a minreduction, of 6 psi., for example, isinitiated, such reduction also takes effect in charging chamber 60 sothat a pressure differential is established between'the opposite sidesof diaphragm-valve member 62. Due to the relatively large pressure areason the respective opposite sides of diaphragm-valve 62, even the initialeffect of such a small pressure reduction and the resulting smallpressure differential therefrom is sufficient for causing saiddiaphragm-valve, and therefore the aperture 63 therein, to be pressedagainst spring housing 89 to insure closure of said apertureandprevention of backfiow therethrough. When'the reduction of 6 psi.reaches its full effect, the resulting pressure differential between theopposite sides of diaphragmvalve 62 is sufficient to cause furtherleftward movement of said diaphragm-valve and compression of spring 90in spring housing 89, which is thereby moved to the left along withlever 88. Pistons 74 and.75 of valve devices 64 and 65 are also moved tothe left until contact is made with check valves 77 and 78 to firstclose axial passageways 84 and 85 and then open said check valves,respectively. Chamber 44 of pneumaticto-hydraulic converter C is thuscommunicated with auxiliary reservoir 57 via passageways 67 and 68, andbrake pipe 58 is communicated with pneumatic pressure chamber 25 ofgravitational braking force converter B via passageway 59, chargingchamber 60, passageway 69, unseated check valve 78, and passageways and71.

The increased pneumatic pressure in chamber 44 of pneumatic-to-hydraulicpressure converter C acts on via passageway 52, supply chamber 47,unseated check valve 49, and conduit 19 to the hydraulic fluid in masterbrake cylinder 18, which tends to exert an upward force on piston 17 andthe adjacent end of lever 14. Since upward movement of piston 17 and theadjacent end of lever 14 is resisted by the spring-biased pressuredevice 16, the pressure acting on hydraulic fluid in conduit 19 istransmitted via said conduit to the brake cylinder (not shown) formoving the brake shoes (not shown) toward the wheel (not shown) for forclosing the gap between the shoes and the wheel.

Pressurized hydraulic fluid in supply chamber 47 of section D also actson the adjacent side of piston 53,

.and is sufficient for overcoming the opposing force of spring 56 tocause said piston to' be moved to the left out of contact with valvestem 52. Since, at this stage, hydraulic pressure is the same on bothsides of check valve 49, spring 51 is effective for seating said checkvalve on valve seat 50. Moreover, the hydraulic pressure acting in brakecylinder conduit 19 is sufficient for maintaining the brake shoes (notshown) against the wheel (not shown). When piston 17 of master brakecylinder 18 exerts further pressure on the hydraulic fluid in conduit19, as will hereinafter be explained, seated check valve 49 preventsbackflow of such increased pressure therepast.

Hydraulic pressure acting in chamber 39 is also transmitted viapassageway 40 to hydraulic pressure control chamber 35 of section B,thereby tending to move valve member 33 to the right. But since, at thispoint, pneumatic pressure from brake pipe 58 also prevails in pneumaticpressure chamber 25 (as above described when check valve 78 is'open),such pneumatic pressure along with the force of spring 36 balance theeffect of hydraulic pressure in chamber 35 to maintain said valve memberand therefore drive piston 26 in their respective neutral positions.Spring 36 is of predetermined compression rating so as to provide thedesired results with respect to movement of valve member 33.

The action of the apparatus, as described up to this point, is effectedwhen a min-reduction of 6 psi. of brake pipepressue-is made..This actionresults in bringing the brake shoes'up against the wheel only, and doesnot produce sufficientflforce for effective braking effort.

Notwithstanding further reduction of brake pipe pressure, the action ofthepneumatic pressure drive section E is limited to that abovedescribed. This is so, because the capacity of auxiliary reservoir 57and the pressure area of piston 43 adjacent pneumatic chamber 44 arefixed. Thus, with check valve 77 open, the respective pressure inauxiliary reservoir 57 and in chamber 44 equalize, and, therefore, themaximum pressure that piston 43 can exert on the column of hydraulicfluid in chamber 39 is determined by the maximum pneumatic pressure atwhich said auxiliary reservoir and said pneumatic chamber equalize,which, at the most, may be on the order of 66 psi.

In order to produce an effective brake application subsequently tomovement of the brake shoes into contact with the wheel, as abovedescribed, a further reduction, or what may be called a servicereduction, of pressure in brake pipe 58 is effected to a preselecteddegree in excess of the min-reduction of 6 psi. As will be explained indetail, the degree of service reduction determines the position offulcrum member relative to operating lever 14 in the gravitationalbraking force ratio converter B, thereby establishing the degree ofbraking force applied by the shoes to the wheel.

When a further reduction of brake pipe pressure in excess of 6 psi. iseffected, such reduction also occurs in pneumatic pressure chamber 25 onthe adjacent side of valve member 33 of section B, whereupon hydraulicpressure in hydraulic chamber 35 on the opposite side of said valvemember is effective for moving the valve member to the right against theopposing force of spring 36 and the residual pneumatic pressure inchamber 25. The amount of rightward movement of valve member 33, ofcourse, is determined by the degree of pressure differential establishedbetween the hydraulic pressure side and the pneumatic pressure side, asaffected by the effects of spring 36. Spring 36 is calibrated such thatthe valve member 33 is permitted to move to the right to an extent thatpermits radial opening 31 only on piston rod 23 to be temporarilyuncovered, whereby pressurized hydraulic fluid (at 66 psi.) may flow viaaxial passageway into chamber 38 on the left side of drive piston 26.(If valve member 33 moved sufficiently to the right to uncover opening32 also, it will be noted that such an amount of movement would alsouncover diametrally oppositely disposed opening 28 in piston rod 23.Uncovering of opening 28 would allow pressurized hydraulic fluid inchamber and consequently in chamber 38 to escape via said opening,recess 27, and opening 29 into atmospheric hydraulic chamber 13 andthereby become depressurized and ineffective for moving and retainingdrive piston 26 to a rightward position.) I

The hydraulic pressure differential between the two sides of drivepiston 26 is made possible by the fact that the pressure area on theright side of siad drive piston is smaller than the pressure area on theleft side thereof by an amount equal to the cross-sectional area ofpiston rod 23. Drive piston 26 thus moves the entire fulcrum member 20to the right to an operative position but only to the extent thatopening 31 is closed and opening 32 is held short of registering withannular groove 35 in said valve member. With both openings 31 and 32lapped off by valve member 33, further flowv of pressurized hydraulicfluid into chamber 38 is cut off, and at the same time escape ofpressurized hydraulic fluid from chamber 38 into recess 27 andatmospheric hydraulic chamber 13 is prevented. At this point allopposing forces acting on drive piston 26 and valve member 33 arebalanced, and the operative position of fulcrum member 20 isestablished. The position'thus as- 'sumed by fulcrum member 20determines the position of rollers 21 on lever l4 and, therefore, thefulcrum point thereof.

With the fulcrum point of lever 14 thus established, the gravitationalforce transmitted through ransfer piston 11 acts on the adjacent end ofsaid lever to set up a clockwise moment, as viewed in the drawing, aboutthe fulcrum point, whereby the opposite end of said lever bearsdownwardly on piston 17 of master brake cylinder 18 for transferring aforce therethrough onto hydraulic fluid in brake cylinder conduit 19proportional to said gravitational force at a ratio determined by thelocation of the fulcrum rollers 21 and the relative lengths of themoment arms thus established. The

degree of force thus exerted by piston 17 on the hydraulic fluid inconduit 19 determines the degree of effective braking pressure exertedby the brake shoes on the wheel.

It should also be noted at this point that the increased pressure on thehydraulic fluid in conduit 19 causes check valve 49 to firmly seat onvalve seat 50 and thereby prevent backflow of highly pressurizedhydraulic fluid to chamber 39 of the pneumatic-to-hydraulic pressureconverter C.

If it is desired to increase the braking effort, a further reduction ofpressure in brake pipe 58 is effected which, in the manner abovedescribed, causes the fulcrum 'member 20 and therefore the fulcrum oflever 14 to be moved further to the right and thus proportionallyincrease the degree of gravitational force transferred to the masterbrake cylinder 18. Since the compression rate of spring 36 is constant,the fulcrum member 20 is moved to the right for a limited increment eachtime a brake pipe pressure reduction is made. The braking force, or theratio of gravitational force to the force delivered by master brakecylinder 18, increases each time the fulcrum member 20 moves rightwardlyto a new position. Thus, when fulcrum rollers 21 are centered on lever14 midway between the two ends thereof, the gravitational force at theend of lever 14 adjacent transfer piston 11 is equal to the forcedelivered by the opposite end of said lever to master brake cylinder 18.

Although, as above set forth, the degree of braking force is indirectlyaffected by the degree of brake pipe pressure reduction in that theposition of fulcrum member 20 relative to lever 14 is established when abrake pipe pressure reduction is made, it should be apparent that,unlike conventional air brake apparatus, the degree of braking appliedat the vehicle wheel is not proportional to the degree of brake pipepressure reduction, but rather is proportional to the degree ofgravitational force transmitted to the master brake cylinder device 18at a ratio established by the position of the fulcrum member 20. Inaccordance to the object of the invention, therefore, any verticaloscillations of the wheel due to the condition of the running surfacecauses corresponding variations in the deflection of load spring 4 and,therefore, in the gravitational forces transmitted through thetransmission section A. Such variations of gravitational force arereflected in the transmittal thereof, through the gravitational brakingforce ratio converter section B, to the master brake cylinder 18. Thus,the force acting on piston 17 of master brake cylinder 18 is constantlychanging or being adjusted to correspond to the variations of thegravitational force prevailing from instant to instant, thereby varyingthe braking force acting on the wheel accordingly. Excessive braking andconsequent wheel-sliding is thus prevented.

In order to release the brakes, either partially or completely, pressurein brake pipe 58 is increased accordingly, such increase also occurringin charging chamber 60 of section E and pneumatic pressure chamber 25 ofsection B. The increased pneumatic pressure in chamber 25, acting withspring 36, is effective for moving valve member 33 to the left untilopening 32 in piston rod 23 registers with annular groove 37 in saidvalve member thereby releasing hydraulic fluid in chamber 38 toatmospheric hydraulic chamber 13 via passageway 30, opening 32,'annulargroove 37, radial opening 28, recess 27, and opening 29. Hydraulic fluidon the right side of drive piston 26 being at the pressure prevailing inchamber 39 forces said drive piston to the left to a position at whichvalve member 33 again laps off the openings 31 and 32. Accordingly,fulcrum member 20 is moved leftwardly a corresponding amount, thusreducing the force acting on master brake cylinder 18 and consequentlythe braking force at the vehicle wheel.

Although, in this manner, pressure in brake pipe 58 may continue to beincreased until fulcrum member 20 resumes its neutral position in whichthe vehicle brakes, for all practical purposes, are completely released,the brake shoes are not withdrawn away'from the wheel until brake pipepressure is restored to a value of approximately 65 psi., for example.With brake pipe pressure at 65 psi., the pressure differential betweenthe opposite sides diaphragm-valve 62 is dissipated, and spring 90 iseffective for returning lever 88, along with pistons 74 and 75, torespective normal positions in which check valves 77 and 78,respectively, are reseated or closed.,With check valves 77 and 78reseated and pistons 74 and in their normal positions, pneumaticpressure in chamber 44 is released to atmosphere viapassageways 68 and84, and atmospheric port 86, and pneumatic pressure in chamber 25 isreleased via passageways 71, 70, and 85, and atmospheric port 87.

Subsequent to this action, the pressure on hydraulic fluid in chamber39, and therefore in supply chamber 47 of section D, is released so thatspring 56 moves piston 53 into contact with valve stem 52, which resultsin unseating or opening of check valve 49. With check valve 49 unseated,hydraulic fluid in conduit 19 is depressurized and forced back tochamber 39 of section C by action of the return spring (not shown) inthe brake cylinder (not shown), thus withdrawing the brake shoescompletely away from the wheel.

As drive piston 26 and valve member 33 move to their respective neutralpositions, hydraulic fluid in chamber 38 flows through passageway 30,opening 32, annular groove 37, opening 28, recess 27, and opening 29into hydraulic fluid storage chamber 13.

With chamber 49 at atmospheric pressure, spring 46 moves piston 43 toits uppermost limit and thereby causes hydraulic fluid to be drawnthrough check valve 42 from chamber 13 into chamber 39 for maintaining asolid column of fluid therein.

Actually check valve device 66 and emergency reservoir 72 are notconsidered essential to the present invention, and, therefore, itsuffices to say that thepurpose of said emergency reservoir is toprovide a volume to which brake pipe pressure may be diverted foraccelerating brake pipe pressure reduction during the initial phase ofbraking action. As above noted, when a brake pipe pressure reduction iseffected, check valve 78 is unseated to connect chamber 25 of section Bto brake pipe 58. And since check valve 79 is held unseated by brakepipe pressure acting on piston 76, reservoir 72 is thus connected withchamber 25 via unseated check valve 79 and passageways 71 and 73. Thecapacity of emergency reservoir 72 is selected to provide a maximumpressure reduction in relation to the capacity of brake pipe 58. Thus,when reservoir 72 is connected to brake pipe 58, as above set forth, therate of reduction of brake pipe pressure is increased rapidly to themaximum permitted during a minimum reduction. This also acceleratesreduction throughout the entire train. Spring 82 acting on check valve79 is calibrated so as to reseat said check valve and prevent backflowfrom reservoir 72 following a brake pipe pressure reduction and flow ofsuch pressure into said reservoir, when the pressure in brake pipe 58and in said reservoir equalize at approximately 66 psi., for example.When pressure in brake pipe 58 is restored to a normal full charge, asabove noted, of 72 psi., piston 75 acts to unseat check valve 79.

Having now described the invention, what we claim as new and desire tosecure by Letters Patent, is:

1. Brake control apparatus for use on a vehicle having spring supportmeans interposed between a sprung portion and an unsprung portion of thevehicle, said brake control apparatus comprising:

a. first means including a fluid medium for exerting braking force onthe vehicle in accordance with the pressure applied to the fluid medium;

b. fulcrumed lever means having one end'engaging said first means forapplying pressure to said fluid medium according to a moment establishedabout the fulcrum of said lever means;

c. second means for transmitting gravitational force of the vehicle tothe other end of said lever means;

d. fulcrum means including a fulcrum member positionally adjustablerelative to the longitudinal axis of said lever means for determiningthe fulcrum point dividing said lever means into moment arms andconsequently establishing the degree of pressure applied by said one endof said lever means on the fluid medium relative to the gravitationalforce acting on said other end of said lever means ata ratio determinedby said moment arms; and

e. operator control means selectively operable for actuating saidfulcrum means and setting the position of said fulcrum member relativeto said lever means.

- 2. Vehicle brake control apparatus, as set forth in claim 1, whereinsaid second means comprises linkage means operablyinterposed between thesprung and unsprung portions of the vehicle, said linkage means beingoperably responsive to deflections of the spring support means fortransmitting said gravitational force to said other end of said levermeans at a degree corresponding to the amount of deflection of thespring support means at any given instant.

3. Vehicle brake control apparatus, as set forth in claim 2 wherein saidlinkage means comprises:

a. a torque rod axially rotatably supported on the sprung portion of thevehicle;

b. a pair of torque arms axially spaced on said torque rod inperpendicular relation thereto and each having one end fixed to saidtorque rod for rotation therewith; and

c. a connecting rod for connecting the end opposite said one end of oneof said torque arms to the unsprung portion,

d. the other of said torque arms having the end opposite its said oneend in operable engagement with said other end of said fulcrumed levermeans for exerting said gravitational forcevthereon.

4. Brake control apparatus, as set forth in claim 1, wherein said firstmeans comprises a master cylinder device including a pressure pistonengaged by said one end of said fulcrumed lever means for applying saidpressure on said fluid medium through said pressure piston.

5. Brake control apparatus, as set forth in claim 1, wherein saidfulcrum member normally occupies a neutral position in which saidfulcrum point coincides with said other end of said fulcrumed lever"means so as to transmit no pressure at said one end of said levermeans, said fulcrum member being operable respon-' sively to fluidpressure out of said neutral position to a plurality of operativepositions in which said fulcrum point is established according to thedegree of fluid pressure differential established by, said operatorcontrol means and acting on the fulcrum member.

6. Brake control apparatus, as set forth in claim 5,

further characterized by biasing means for retaining said one end ofsaid fulcrumed lever means in contacting engagement with said firstmeans at all times.

. 7. Brake control apparatus, as set forth in claim 5, wherein saidfulcrum means includes a drive piston for operating said fulcrum member,said drive piston being subjected on one side to a constant fluidpressure and on the opposite'side to a variable fluid pressure, saidconstant fluid pressure acting on said one side of said drive pistonbeing effective upon selective variation of said variable fluid pressureby said operator control means for establishing a fluid pressuredifferential across said drive piston to effect operation of saidfulcrum member to one of its-said plurality of operative positionsaccording to the degree of said fluid pressure differential. I

8. Brake control apparatus, as set forth in claim 7,

wherein said constant fluid pressure acting on said one furthercharacterized by pneumatic-to-hydraulic pressure converter meansincluding a floating piston having one side thereof inpressure contactwith hydraulic fluid acting on said one side of said drive piston andthe other side subject to a constant pneumatic pressure established bythe operator control means.

10. Brake control apparatus, as set forth in claim 9,

wherein said operator control means further comprises:

a. a brake pipe normally charged toa preselected pneumatic pressure; a

b. a fixed volume chargeable with pneumatic pressure from said brakepipe;

c. diaphragm-valve means interposed between said brake pipe and saidfixed volume and effective upon equalization of pneumatic pressure onopposite sides thereof for automatically isolating said brake pipe fromsaid fixed volume upon equalization of pneumatic pressure therebetweenat saidpreselected pneumatic pressure;

d. a first check valve device interposed in first passage means forcontrolling communication between said brake pipe and said opposite sideof said drive piston and effective, when in an open position, forestablishing pneumatic brake pipe pressure on said opposite side of saiddrive piston via said first passage means; and

e. a second check valve device interposed in second passage means forcontrolling communication between said fixed volume and said oppositeside of said floating piston and effective, when in an open position,for establishing pneumatic pressure on said opposite side of thefloating piston via said second passage means at a degree equivalent tothat in the fixed volume and consequently on said one side of said drivepiston through the hydraulic fluid,

f. said first and second check valve devices being operablesimultaneously to their respective open positions by saiddiaphragm-valve means upon reduction of brake pipe pressure acting onone side thereof to a pressure less than a certain degree.

11. Brake control apparatus, as set forth in claim 10,

further characterized by first biasing means effective forsimultaneously Operating said first and second check valve devices torespective closed positions, in which said communications are cut offand said first and second passage means are opened to atmosphere, uponrestoration of brake pipe pressure acting on said one side of thediaphragm-valve means to a pressure vices to their respective closedpositions.

1. Brake control apparatus for use on a vehicle having spring supportmeans interposed between a sprung portion and an unsprung portion of thevehicle, said brake control apparatus comprising: a. first meansincluding a fluid medium for exerting braking force on the vehicle inaccordance with the pressure applied to the fluid medium; b. fulcrumedlever means having one end engaging said first means for applyingpressure to said fluid medium according to a moment established aboutthe fulcrum of said lever means; c. second means for transmittinggravitational force of the vehicle to the other end of said lever means;d. fulcrum means including a fulCrum member positionally adjustablerelative to the longitudinal axis of said lever means for determiningthe fulcrum point dividing said lever means into moment arms andconsequently establishing the degree of pressure applied by said one endof said lever means on the fluid medium relative to the gravitationalforce acting on said other end of said lever means at a ratio determinedby said moment arms; and e. operator control means selectively operablefor actuating said fulcrum means and setting the position of saidfulcrum member relative to said lever means.
 2. Vehicle brake controlapparatus, as set forth in claim 1, wherein said second means compriseslinkage means operably interposed between the sprung and unsprungportions of the vehicle, said linkage means being operably responsive todeflections of the spring support means for transmitting saidgravitational force to said other end of said lever means at a degreecorresponding to the amount of deflection of the spring support means atany given instant.
 3. Vehicle brake control apparatus, as set forth inclaim 2 wherein said linkage means comprises: a. a torque rod axiallyrotatably supported on the sprung portion of the vehicle; b. a pair oftorque arms axially spaced on said torque rod in perpendicular relationthereto and each having one end fixed to said torque rod for rotationtherewith; and c. a connecting rod for connecting the end opposite saidone end of one of said torque arms to the unsprung portion, d. the otherof said torque arms having the end opposite its said one end in operableengagement with said other end of said fulcrumed lever means forexerting said gravitational force thereon.
 4. Brake control apparatus,as set forth in claim 1, wherein said first means comprises a mastercylinder device including a pressure piston engaged by said one end ofsaid fulcrumed lever means for applying said pressure on said fluidmedium through said pressure piston.
 5. Brake control apparatus, as setforth in claim 1, wherein said fulcrum member normally occupies aneutral position in which said fulcrum point coincides with said otherend of said fulcrumed lever means so as to transmit no pressure at saidone end of said lever means, said fulcrum member being operableresponsively to fluid pressure out of said neutral position to aplurality of operative positions in which said fulcrum point isestablished according to the degree of fluid pressure differentialestablished by said operator control means and acting on the fulcrummember.
 6. Brake control apparatus, as set forth in claim 5, furthercharacterized by biasing means for retaining said one end of saidfulcrumed lever means in contacting engagement with said first means atall times.
 7. Brake control apparatus, as set forth in claim 5, whereinsaid fulcrum means includes a drive piston for operating said fulcrummember, said drive piston being subjected on one side to a constantfluid pressure and on the opposite side to a variable fluid pressure,said constant fluid pressure acting on said one side of said drivepiston being effective upon selective variation of said variable fluidpressure by said operator control means for establishing a fluidpressure differential across said drive piston to effect operation ofsaid fulcrum member to one of its said plurality of operative positionsaccording to the degree of said fluid pressure differential.
 8. Brakecontrol apparatus, as set forth in claim 7, wherein said constant fluidpressure acting on said one side of said drive piston is hydraulic fluidpressure and said variable fluid pressure acting on the opposite side ofsaid drive piston is pneumatic fluid pressure.
 9. Brake controlapparatus, as set forth in claim 8, further characterized bypneumatic-to-hydraulic pressure converter means including a floatingpiston having one side thereof in pressure contact with hydraulic fluidacting on said one side of said drive piston and the other side subjectto a Constant pneumatic pressure established by the operator controlmeans.
 10. Brake control apparatus, as set forth in claim 9, whereinsaid operator control means further comprises: a. a brake pipe normallycharged to a preselected pneumatic pressure; b. a fixed volumechargeable with pneumatic pressure from said brake pipe; c.diaphragm-valve means interposed between said brake pipe and said fixedvolume and effective upon equalization of pneumatic pressure on oppositesides thereof for automatically isolating said brake pipe from saidfixed volume upon equalization of pneumatic pressure therebetween atsaid preselected pneumatic pressure; d. a first check valve deviceinterposed in first passage means for controlling communication betweensaid brake pipe and said opposite side of said drive piston andeffective, when in an open position, for establishing pneumatic brakepipe pressure on said opposite side of said drive piston via said firstpassage means; and e. a second check valve device interposed in secondpassage means for controlling communication between said fixed volumeand said opposite side of said floating piston and effective, when in anopen position, for establishing pneumatic pressure on said opposite sideof the floating piston via said second passage means at a degreeequivalent to that in the fixed volume and consequently on said one sideof said drive piston through the hydraulic fluid, f. said first andsecond check valve devices being operable simultaneously to theirrespective open positions by said diaphragm-valve means upon reductionof brake pipe pressure acting on one side thereof to a pressure lessthan a certain degree.
 11. Brake control apparatus, as set forth inclaim 10, further characterized by first biasing means effective forsimultaneously operating said first and second check valve devices torespective closed positions, in which said communications are cut offand said first and second passage means are opened to atmosphere, uponrestoration of brake pipe pressure acting on said one side of thediaphragm-valve means to a pressure exceeding said certain degree. 12.Brake control apparatus, as set forth in claim 10, wherein the degree ofpneumatic pressure acting on said opposite side of said drive piston isvariable according to the prevailing degree of brake pipe pressureduring such time that said first check valve device is in its said openposition.
 13. Brake control apparatus, as set forth in claim 11, furthercharacterized by second biasing means for restoring said fulcrum memberto its said neutral position upon operation of said first and secondcheck valve devices to their respective closed positions.